Many methods exist for coating substrates with solid materials. For example, paint sprayers and electrostatic spray guns atomize particles to a very fine mist for application to a desired surface. Application of larger solid particles can be significantly more difficult. The larger particle sizes tend to cause clogging in the machinery.
In the food industry, it is often desirable to apply a solid topping to a base product. Typically, the material is applied by force of gravity. U.S. Pat. No. 4,419,953 discloses an apparatus for applying seasoning to a snack product. The seasoning is simply allowed to fall from an outlet by force of gravity in a continuous stream onto the snack product. Additionally, air currents are provided to force excess seasoning upward to coat the underside of the snack product. Excess seasoning that does not coat the product is collected and recycled through the system. Such a system tends to be extremely messy and inefficient.
U.S. Pat. No. 4,715,275 discloses an apparatus for producing frozen confections including edible particulate material. The particulate material travels from a hopper through conduits and falls onto the confections by force of gravity. Measured quantities of the material are fed through the conduit by timed, intermittent activation of a vibrator that releases the material.
Most commercial food processing systems are continuous systems wherein the food product is conveyed through the system. Such conveyance, particularly at high throughputs, creates air currents that can disrupt the smooth, uniform nature of a material that is falling by force of gravity to be applied to the food product. The material tends to “float” down to the substrate. The air currents caused by conveyance of the food products however, diverts the smaller particles of the material from the substrate. This results in wasted coating material, as much of the particulate material often ends up on the floor or otherwise missing the intended substrate target. This loss in material further necessitates the overfeeding of the material to apply a minimum amount of the material onto the surface of the substrate. This method is not very cost-efficient, particularly because many edible seasoning particulates tend to be relatively expensive compared to the underlying substrate.
Other methods besides the use of gravity have also been used. U.S. Pat. No. 4,640,219 discloses an apparatus for the application of coating material onto the side surfaces of elongated food products. An applicator nozzle and nozzle opening portion of the apparatus correspond to the side surfaces of the elongated food product. The food product to be coated is passed before nozzles discharging horizontally impelled coating material from a coating material supply source that meters desired amounts of coating material to a blower device.
U.S. Pat. No. 6,129,037 discloses a bakery dough flour applicator. A flour supply reservoir or hopper provides a source of flour by means of a transfer assembly to an aeration unit which mixes a predetermined amount of flour with a preset flow of air provided by an auxiliary blower. The airborne flour stream created by the aeration unit is then routed through a distribution network that delivers the stream of airborne flour to an enclosure mounted on the dough processing path. The airborne flour enters the open ended flour applicator enclosure through a series of spray nozzles that direct the flow of airborne flour toward the path of the dough pieces passing along a portion of the processing path, which can take the form of a surface conveyor or a downwardly inclined ramp within the enclosure. The spray nozzles form a cloud or turbulence of airborne flour in the environment of the dough pieces which is confined by the interior surfaces of the flour applicator enclosure and the processing path. The airborne flour forming the turbulence adheres to the sticky exterior surfaces of passing dough pieces and also tends to coat the surfaces of the processing equipment exposed within the enclosure, such as the enclosure interior side walls and the ramp.
As none of the conventional apparatuses accurately and precisely delivers edible particulate toppings in desired patterns to substrates, it is still desired to build an improved apparatus.